Merge pull request #4713 from crobibero/robots

(cherry picked from commit a3a7467f49)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>

Jellyfin.Server/Middleware/RobotsRedirectionMiddleware.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+
+namespace Jellyfin.Server.Middleware
+{
+    /// <summary>
+    /// Redirect requests to robots.txt to web/robots.txt.
+    /// </summary>
+    public class RobotsRedirectionMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly ILogger<RobotsRedirectionMiddleware> _logger;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RobotsRedirectionMiddleware"/> class.
+        /// </summary>
+        /// <param name="next">The next delegate in the pipeline.</param>
+        /// <param name="logger">The logger.</param>
+        public RobotsRedirectionMiddleware(
+            RequestDelegate next,
+            ILogger<RobotsRedirectionMiddleware> logger)
+        {
+            _next = next;
+            _logger = logger;
+        }
+
+        /// <summary>
+        /// Executes the middleware action.
+        /// </summary>
+        /// <param name="httpContext">The current HTTP context.</param>
+        /// <returns>The async task.</returns>
+        public async Task Invoke(HttpContext httpContext)
+        {
+            var localPath = httpContext.Request.Path.ToString();
+            if (string.Equals(localPath, "/robots.txt", StringComparison.OrdinalIgnoreCase))
+            {
+                _logger.LogDebug("Redirecting robots.txt request to web/robots.txt");
+                httpContext.Response.Redirect("web/robots.txt");
+                return;
+            }
+
+            await _next(httpContext).ConfigureAwait(false);
+        }
+    }
+}